Mechanical Characterization and Modeling of Direct Metal Laser Sintered Stainless Steel GP1

The additive manufacturing (AM) process is unique in that it can facilitate anisotropy because of the layer-by-layer deposition technique intrinsic to this process. In order to develop a component for a desired application, it is necessary to understand the mechanics that facilitate this material behavior. This study investigates how build orientation affects the mechanical performance of as-built direct metal laser sintered (DMLS) stainless steel (SS) GP1 (also referred to as 17-4PH) through strain-controlled monotonic tension and completely reversed low-cycle fatigue (LCF) testing. The anisotropic behavior of DMLS SS GP1 is assessed for samples built along the horizontal plane. Fracture surfaces were found to exhibit ductile responses that were consistent with the σ–ε curves. Constitutive models (i.e., Ramberg–Osgood, Hahn) based upon linear elasticity and nonlinear plasticity are presented and used to simulate the monotonic discontinuous stress–strain yielding response of this material, which are found to be in agreement with the experimental data. A collection of low-cycle fatigue tests reveals initial strain hardening to stabilization, followed by softening to fracture. Tensile and fatigue material constants determined from experimental findings are also presented in this study. Plasticity effects on the life of varying build orientations are explored.